This invention relates in general to antifriction bearings and, more particularly, to a bearing having means for providing supplemental lubrication to critical surfaces within the bearing.
The tapered roller bearing in its most basic form includes an inner race or cone, an outer race or cup, and tapered rollers arranged in a single circular row between the cone and cup. The tapered rollers along their side faces contact tapered raceways on the cup and cone. This geometry enables the tapered roller bearing to take both radial and axial or thrust loads, making it ideally suited for many machine applications. But the geometry also causes each roller to experience a slight axially directed force when the roller transfers a radial load, and this force must be resisted if the bearing is to remain intact. Thus, to counteract the axial expulsion force, the cone of the typical tapered roller bearing has a thrust rib which projects radially beyond the large end of the cone raceway where it presents an abutment face against which the large end faces of the rollers bear.
When the cone rotates within the cup or the cup about the cone, the tapered rollers roll along the raceways. Essentially true rolling contact exists between the raceways and the tapered side faces of the rollers, and hence little friction develops along the raceways. But the large end faces of the rollers sweep or slide along the abutment face of the thrust rib, generating considerably more friction at this location. In many tapered roller bearings grease packed into the bearing on assembly reduces the friction sufficiently to avoid damage to the bearing. Others are furnished with a constant flow of liquid lubrication. In this regard, a tapered roller bearing inherently pumps its lubricants from the small ends of the raceways to the large ends of those raceways and thus will deliver the lubricant to the critical abutment face on the thrust rib.
Despite the measures to provide lubrication, tapered roller bearings occasionally operate with insufficient lubrication. Even though the condition may only be momentary, as it sometimes is, the sliding contact between the large end faces of the rollers and the abutment face of the thrust rib may be enough to cause significant damage.
To be sure, others have already addressed this problem. For example, some tapered roller bearings have hard coatings on the abutment surfaces of their thrust ribs and the large end faces of their rollers. Other bearings have porous metal thrust ribs which are impregnated with oil and release it to the large end faces of the rollers when the bearing loses its normal supply of lubrication. Still others have complex cages which carry lubricant and release it when necessary, not to the thrust rib and roller end faces, but to the roller side faces. Generally speaking, these attempts significantly increase the cost and complexity of the bearings.
The present invention resides in a roller bearing having lubricating means which releases a lubricant to the abutment face on a rib which guides the rollers of the bearing, with the release of the lubricant occuring when this critical surface area loses its normal supply of lubrication. The lubricating means may also release lubrication to the end faces of the rollers when they become starved for lubrication. The lubricating means may take the form of a ring having a band located opposite the end faces of the rollers and tabs projecting from the band and located opposite the abutment face of the rib.